1. Field of the Invention
The present invention relates to aircraft doors and associated mechanisms. More particularly, this invention pertains to a plug door system adapted for use with double decked fuselage configurations.
2. Description of the Prior Art
Plug-type doors are inwardly-opening devices designed to fit into ingress and egress openings of an aircraft's fuselage. Cabin pressure seals the door shut against a door jamb. The outer surface or skin of the door is designed to form a substantially smooth, continuous and uninterrupted exterior surface with the fuselage. When open, such doors are arranged to work inwardly and upwardly into the aircraft fuselage and to slide along tracks mounted on the interior thereof. Such doors are electrically operated in some cases and manually operated in others.
A representative plug door mechanism of the above-referenced type is disclosed in U.S. Pat. No. 3,585,757 entitled "Overhead Opening Plug Door", property of the assignee herein. That patent discloses a system suitable for adaptation to an aircraft, such as the well-known DC-10, whose fuselage encloses a cabin that includes an arrangement of crew and passenger seats attached to a common planar floor. The door includes mechanisms for retracting it directly above the door jamb and into the wall of the fuselage. Tracks are mounted within the fuselage for receiving elements associated with the door. Power-actuated cables move the door along the tracks. The door is roller-mounted to the tracks which possess a curvature. The curvature essentially traces that of the fuselage. Push-pull rods and cam linkages are provided for operating the door between its open and closed positions.
While mechanisms of the above described type provide an adequate means for operating and storing the door in a reliable and unobstructive manner, they are not suitable for aircraft of the so-called double-decked type that include a second, upper deck or floor that divides the interior of the fuselage into two vertically stacked levels. This increases passenger capacity and comfort substantially by providing efficient utilization of overhead space. FIG. 1 is a side elevation view of a representative aircraft of the double-decked type while FIG. 2 is a cross-sectional view of that aircraft taken at line 2--2 of FIG. 1. A plurality of lower level door jambs 12 are provided for ingress to and egress from the fuselage 14. Each Door jamb 12 receives a plug door 16. As can be seen in FIG. 2, the interior of the fuselage 14 is divided into an upper cabin 18 and a main cabin 20 by an upper floor 22. The floor 22 may comprise a planar array of J-beams and associated structures. The upper floor 22 supports a set of passenger seats 24 to increase passenger capacity beyond that otherwise attainable. A lower floor 26 supports a set of passenger seats 28 within the main cabin 20.
While offering an efficient use of fuselage height, structural considerations reduce the availability of usable fuselage storage space above the door jambs 12 in a double-decked aircraft.